This invention relates to cheese moulds and is concerned more particularly with drainage plates for lining the walls of cheese moulds.
In the manufacture of cheddar or other hard cheese, crumbled cheese curd is mixed with salt and possibly other additives and the curd mixtures subjected to pressure in a mould to press whey out of the curd and thereby form a block of natural cheese. For convenience the mixture of curd and other additives will be referred to hereinafter as curd. The moulds at present in commercial use are generally lined with drainage plates formed with a large number of small apertures spaced evenly over the whole area of the plates, the whey pressed out of the curd passing through the apertures and draining through passages formed between the plates and the walls of the mould. The inside surface of the drainage plates, that is the surface facing the curd, must be smooth to enable the compressed block to slide out of the mould at the end of the pressing operation.
It is known to form drainage plates by punching narrow rectangular portions of a flat plate out of the plane of the plate so as to form narrow strips the ends of which are integral with the remainder of the plate but the center portions of which are spaced from the plate to form slots between the plate and the side edges of the centre portion of the strips. The strips are arranged parallel to one another in rows with the strips in each row offset laterally relative to the strips in the adjacent rows. In use, the drainage plates are fitted in the mould with the side having the recesses formed by punching out the narrow strips facing the curd, and the strips aligned in the direction in which the compressed block of curd slides upon removal from the mould. When the curd is subjected to pressure to expel the whey, the curd is of course forced in to the recesses in the drainage plates and tends to become jammed therein. The force necessary to slide the block out of the mould must then be sufficient to sever the curd in the recesses from the remainder of the block of curd. Also the curd left in the recesses tends to clog up the drainage slots when the next mass of curd is compressed in the mould.
The amount of the force required to overcome the frictional resistance between a block of curd and drainage plates is particularly important in the cheese making apparatus described in U.S. Pat. No. 3,468,026 in the name of G. M. Robertson and G. K. Charles in which the crumbled curd is fed at a sub-atmospheric pressure into a hollow column which is in effect a mould for the cheese, the walls of the column consisting of drainage plates so that the curd is formed into a pillar the weight of which is relied on to provide the pressure for expelling whey from the curd in the bottom of the pillar and for displacing the pillar downwards in the column. The frictional resistance between the pillar of curd and the drainage plates depends upon the texture and variety of the cheese being made, and if the frictional resistance is high there is a risk that the pillar of curd may fracture.